41 per cent were unaware of the link between what they eat and the disease.

Only around one in three people knew that eating processed meat increased their cancer risk while 44 per cent were unaware that being overweight was another risk factor.

A total of 42 per cent knew that not taking enough exercise or being physically active increased their risk of cancer.

Now, here’s why we’re scratching our heads a bit.

A paradox

On an almost weekly basis, we’re asked to comment on all manner of media stories about the links between a given food or behaviour and cancer. The theme recurs time and time again, in slightly different formats, based on evidence ranging from the anecdotal to the watertight.

These ‘X causes/prevents cancer’ stories appear in all newspapers. They echo round the airwaves. You can see them on the telly. And we try to dissect them as far as possible on this blog.

As Ben Goldacre over at the Bad Science blog wryly notes, it’s as if certain sections of the media are on a

Sisyphean task of dividing all the inanimate objects in the world into the ones that either cause or cure cancer

So why do the surveys suggest that no-one’s listening to the key messages?

We’re genuinely a bit puzzled. But we have an inkling of an idea.

Public reactions

One of the things we’ve noticed in the ‘have your say’ comments section of many news websites is the following complaint, which we’ll paraphrase:

“There’s no point in believing any of this, because these ‘experts’ change their mind every week”

It seems that media reporting of ‘x causes cancer’ stories, in all its keenness and enthusiasm to get the message across, and in its intensity and frequency, is having precisely the opposite effect.

This is an unfortunate state of affairs.

‘Ask the experts’?

One possible reason why this is happening, we think, is that the concept of ‘expert knowledge’ has become diluted.

For example, the ‘coffee & leukaemia‘ story from a few weeks back was based on research that hadn’t even been done.

Similarly, other stories are frequently based on studies in animals, or on cells in a lab. Others report the first time a phenomenon has been found, and such findings need to be repeated to be certain.

Of course all these studies were carried out by professional scientists – ‘experts’. But, importantly, that doesn’t mean their findings constitute the sort of evidence that we should use to guide our everyday behaviour.

On the other hand, consider the mammoth, careful, painstaking review of expert evidence contained in the WCRF report on diet and cancer from November 2007.

This report was written collaboratively by many scientists. It was not only based on research that had been done, but a whopping 7000 individual research papers that had been carefully reviewed, weighed, collated and assessed (and the reaction to which, Ed wrote a great post about).

This confusion of ‘everyday science’ with ‘carefully reviewed evidence’ has the effect of hiding the real facts amongst a smog of conjecture. And people seem, if the message boards are anything to go by, irritated and disillusioned. And many seem to have stopped listening altogether.

The evidence

The effect of people’s lifestyles on their risk of cancer is now well documented. The Healthy Living section of our website is full of accurate, reliable advice on reducing the risk of cancer, all based on solid, reliable evidence. These tips have the potential to save lives, but they’re getting lost amid all the surrounding media noise.

The WCRF survey contained a positive note:

The poll did reveal that awareness among the general public is growing, with more people saying they knew of the link between diet and exercise than in a similar survey in 2007.

Could this be due to the fact that the scientific accuracy of media coverage is improving? Or is it because greater access to the Internet means people can access the proper evidence? It’s another interesting question and one that we’ll doubtless explore in future blog posts.

But to sum up, the core messages about cancer and lifestyle aren’t ‘sexy’. There doesn’t appear to be any single food or pill that you can take to prevent the disease.

Cancers are less common amongst people who take regular exercise, have a healthy diet, keep a healthy weight, who don’t smoke, who drink less alcohol, and are sensible in the sun.

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